基于单缸机的快速压缩膨胀装置设计与仿真研究

Design and simulation of a rapid compression andexpansion machine based on a single cylinder engine

为了对内燃机内部流场、点火和燃烧过程开展可视化研究,采用了单缸发动机和可视化定容燃烧弹组合设计方式,对快速压缩膨胀装置进行了设计研究。首先,在此装置上安装了活塞使燃烧室内产生流场,利用了可视化定容燃烧弹观察燃烧室内部流场情况与燃烧进程,利用了NI公司的CompactRIO 9036硬件系统编写控制程序以实现系统控制;其次,调整了初始充气压力以改变点火时刻环境压力,控制了发动机转速以改变流场流速,模拟了不同工况下的燃烧室流场,开展了点火和燃烧过程的可视化研究;最后,进行了流场仿真与点火实验,研究了快压机内部的动态流场以及点火燃烧过程。仿真研究结果表明:控制发动机转速和点火正时可实现点火时刻火花塞附近流速在5.20 m/s~46.25 m/s可变,而环境压力对速度场影响不大。实验结果与仿真结果相符,表明本装置可为强湍流稀薄混合气点火和燃烧过程的可视化研究提供重要支撑。

In order to analyze the internal flow field,visible ignition and combustion process in the internal combustion engine,a study of the design of a rapid compression and expansion machine was executed by the combination design method of a single-cylinder engine and a visible constant volume chamber.Firstly,a piston was installed on the equipment to create dynamic flow filed in the combustion chamber,a visible constant volume chamber was used to observe the dynamic flow field and the ignition and combustion process inside the combustion chamber,the NI CompactRIO 9036 hardware system,was used to program to control the rapid compression and expansion machine system.Secondly,the ambient pressure at the ignition moment was changed by adjusting the initial charge pressure,and the flow velocity was changed by adjusting the engine speed.The flow field of combustion chamber in different operating conditions was simulated.Visible studies on ignition and combustion processes were carried on.Finally,the dynamic flow field simulation and ignition experiments were carried out;the dynamic flow field,the ignition and combustion process inside the rapid compression and expansion machine were studied by means of the flow field simulation and the ignition experiments.The results of flow field simulation research indicate that flow velocity near the spark plug during ignition can be varied from 5.20 m/s to 46.25 m/s by adjusting engine speed and ignition timing,but environmental pressure has little influence on it.The results of ignition experiments research of various operating conditions are consistent with the simulation results,indicating that the machine can provide important support for visualization study of the ignition and combustion process of lean mixture with strong turbulence condition.